Biomedical subjects
Publications and source records attributed to J Johansson.
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A new approach to the error catastrophe theory, proposed by Leslie Orgel, is presented here. Our model is a development of previous models, but differs in several respects: the overall activity is assumed to be dependent on the error level, the effect of errors in the translating system, giving rise to additional errors in the succeeding generation of products, is explicitly included as a special term in our model, and scavenging enzymes are assumed to break down and eliminate products with a loose structure. Their efficiency is dependent on the error level. The model also takes into account the dilution of incorrect ribosomes and enzymes, and is described by a time-dependence in terms of ribosome/enzyme generations. The model and the contribution to the time development are discussed in the light of experiments on E. coli treated with streptomycin.
With the aid of a kinetic model, we have investigated how the adaptation between the various components of the tRNA cycle and the codon frequencies affects the rate of protein synthesis. Depending on the relative amounts of total tRNA, synthetase and ribosomes, the optimal correlations vary between a situation where all tRNA species are either present in equal amounts or are present in amounts proportional to the square-root of the corresponding codon frequencies, and a situation where the amounts of the different tRNA species present are linearly proportional to the codon frequencies.
Subfractionation of the 3 major plasma lipoprotein classes was performed in 20 male patients with symptomatic peripheral vascular disease (PVD) and 18 male healthy controls of similar age and serum lipid levels as the patients in order to investigate if, at comparable levels of total serum lipids, any difference in the distribution or the chemical composition of the lipoprotein subfractions existed between patients and controls. Concentrations of free and esterified cholesterol, triglycerides, phospholipids, apolipoprotein B (apo B) and soluble apolipoproteins did not differ significantly in any lipoprotein subfraction of PVD patients compared to controls. Calculated molecular weights and numbers of lipoprotein particles/ml plasma were also similar in the 2 groups except that there were more heavy LDL particles in the patient group. Plotting concentrations of apo B against cholesteryl ester in the VLDL-D subfraction (Sf 20-100) yielded a linear regression in both groups. The PVD regression line was significantly steeper than that of controls. Calculation of the molecular mass of the various constituents of the VLDL-D fraction in the subjects with the highest content of esterified cholesterol in VLDL-D, where this difference was most pronounced, suggests that this difference was due entirely to a decreased number of cholesteryl ester molecules per lipoprotein particle in PVD. The findings suggest that a disordered metabolism of plasma cholesteryl esters may be present in certain PVD patients.
The amino acid sequence of a large form of inhibin-like peptide in human seminal plasma was determined, and compared with structures reported for similar inhibin preparations and a seminal plasma globulin. The data confirm and correlate previous reports on this form of inhibin-like peptide. The structural comparisons further suggest that the peptide is closely similar to or possibly identical to a sperm-coating antigen reported to be synthesized from prostatic epithelium. This may correlate with non-gonadal origins of inhibin-like material and will help to elucidate the biological roles of inhibin(s).
Trans-membrane helices have often been claimed to show "sidedness" in the distribution of polar and hydrophobic residues. However, an analysis of the statistical distribution of polar residues in randomly generated helices shows that the degree of bias commonly observed in real helices is far from statistically significant. It is concluded that "patchy" distributions of residues in such helices should be interpreted with great care.
It is argued that in order to optimize the achievement of self-control and to evaluate the clinical effects of biofeedback three skills should be included in training and assessment, namely: (1) the ability of voluntary control with external feedback, (2) the ability of voluntary control without external feedback, and (3) the ability to apply the self-control skill in critical situations in everyday life. A review of the literature concerning temperature-biofeedback in the treatment of migraine headaches shows that the research from this point of view is in a rather poor state of affairs and that no definite conclusion can in fact be drawn about the degree of self-control which has been achieved and hence of the ultimate clinical value of biofeedback.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.